Thanks for using the Apple Support Communities. From your post, I understand that your iPhone 7 is not ringing when you get a phone call. I'll be happy to help!
It's great to see that you have already checked to make sure the Ring/Silent switch is not engaged, that Do Not Disturb is off, and that your volume is turned all the way up. Since you're still not getting a ring, I would suggest next checking to make sure your Phone Notifications are set appropriately. To do this, head into Settings > Notifications > Phone. Make sure that "Allow Notifications" is enabled, and that there is a sound option selected under Sounds.
If everything looks right in Notifications, turn the "Allow Notifications" option off, then restart your iPhone as detailed here: Restart your iPhone, iPad, or iPod touch . Then, go back into the Notifications and turn "Allow Notifications" on again and test the ringer.
Are you using a custom ringtone purchased from the iTunes Store? If so, I can also suggest going into Settings > Sounds and seeing if the ringtone plays there. If it does not, re-sync the ringtone from iTunes and try again: Sync your iPhone, iPad, or iPod touch with iTunes on your computer using USB
If you continue to have trouble, don't hesitate to reply back.
Cheers!